lima/ppir: lower fdot in nir_opt_algebraic

The Mali400 pp doesn't implement fdot but has fsum3 and fsum4, which can be used to optimize fdot lowering. fsum2 is not implemented and can be further lowered to an add with the vector components.

Currently lima ppir handles this lowering internally, however this happens in a very late stage and requires a big chunk of code compared to a nir_opt_algebraic lowering.

By having fsum in nir, we can reduce ppir complexity and enable the lowered ops to be part of other nir optimizations in the optimization loop.